The physical dimensions of a disk drive assembly may be described as a "form factor". A form factor is an industry standard of length, width and height dimensions. Alternatively, the length and width dimensions of a disk drive assembly may be referred to together as a lateral form factor area and the height may be referred to as a vertical thickness. A lateral form factor area may, in a 3.5 inch diameter disk drive, be 4.00 inches by 5.75 inches whereas a corresponding vertical thickness may be, for example, 0.5 inches. As the lateral form factor area and vertical thickness of disk drive assemblies has decreased over time, the available area on which to place the required electronic circuitry of the disk drive assembly has also decreased.
Early disk drive assemblies typically had a printed circuit board which extended over substantially the entire lateral area of the form factor. The disk or disks themselves were usually disposed in a sealed enclosure, the bottom surface of the sealed enclosure being disposed to be parallel with the plane of the printed circuit board outside the sealed enclosure. Electronics on this printed circuit board was coupled to a read/write head actuator mechanism inside the sealed housing via a connector which passed through the enclosure. An interface connector on the printed circuit board allowed the disk drive assembly to connect to a system with which the disk drive assembly was to operate.
As disk drive technology progressed, advances in disk drive assemblies were made. One such advance is disclosed in copending and commonly owned U.S. patent application Ser. No. 07/764,590, now abandoned, the subject matter of which is incorporated herein by reference. In the 07/764,590 patent application now abandoned, a disk drive assembly is disclosed in which a printed circuit board is placed in a corner portion of a 4.00 inch by 5.75 inch lateral form factor area enclosure so that the printed circuit board and the electronics disposed on it are located outside of a sealed volume containing the disk(s). This printed circuit board is, in some embodiments, a substantially triangularly shaped printed circuit board which is disposed substantially in the same plane as the plane of a single disk. To enable substantially all the required circuitry except for read/write head preamplification circuitry to be disposed on this relatively small printed circuit board, the integrated circuit chips making up the circuitry are mounted both on both the top surface and also on the bottom surface of the printed circuit board. The added thickness due to the placement of integrated circuit chips on both the top and bottom surfaces of the printed circuit board is accommodated due to the printed circuit board not extending either over or under the disk(s) in the sealed volume. Accordingly, a larger portion of the full vertical thickness of the disk drive assembly is usable for the printed circuit board and its associated integrated circuit chips.
A flexible circuit disclosed in the 07/764,590 patent application is used to couple a read/write head disposed at the end of a load beam to circuitry on the printed circuit board. One end of this flexible circuit attaches to the load beam near the load beam pivot. The flexible circuit passes from the sealed volume and into the corner portion of the enclosure to a first part of a flexible circuit to printed circuit board connector. The printed circuit board, bearing a second part of the flexible circuit to printed circuit connector, is slidable into the corner portion of the enclosure so that the second part of the flexible circuit to printed circuit connector disposed on the printed circuit board can mate with the first part of the flexible circuit to printed circuit board connector disposed on the flexible circuit. With the printed circuit board inserted into the corner portion and with the first and second parts of the flexible circuit to printed circuit board connector mated together, an interface connector disposed along one edge of the printed circuit board is oriented facing outwardly from the disk drive enclosure. This interface connector is usable to couple the disk drive assembly to a system with which the disk drive assembly is to operate.
In order to shrink the form factor of the disk drive assembly still further, from for example a 4.00 inch by 5.75 inch lateral form factor area down to a 2.75 inch by 4.00 inch lateral form factor area, the lateral area of the corner portion is also decreased. This decrease may not provide adequate space for placement of the required integrated circuit chips onto the printed circuit board in the corner portion. With current semiconductor processing technologies, multiple different integrated circuit chips must be used to realize inexpensively and reliably all the required disk drive circuitry. A single semiconductor processing technology has not yet been found which can both inexpensively and also reliably realize the required digital circuitry, analog circuitry, and power circuitry all on a single integrated circuit chip. Moreover, the flexible circuit to printed circuit connector consumes a substantial portion of the scarce surface area of the printed circuit board. Accordingly, it is difficult in reduced form factor area disk drive assemblies to place all the required different integrated circuit chip packages and all the required connectors onto the two surfaces of a printed circuit board in the corner portion of the form factor.